Reservoirs aren’t the field of dreams: Even when we build them, the water doesn’t necessarily come. Statewide reservoir storage plunged to 69% percent below average by the end of September 2022, on the heels of the state’s driest three-year stretch on record.
Proposition 1, approved in 2014, set aside $2.7 billion to fund water storage projects. The three projects eligible to receive funding, which include the controversial Sites reservoir, would increase storage capacity by more than 1.75 million acre-feet, enough to supply more than 6 million households.
How much they would increase the water supply available each year, however, is unclear. Lengthy droughts deplete reservoir storage, and “the average volume of new water from these facilities is small, and costs are high, The Public Policy Institute of California warned in 2018
Many reservoirs in California do double duty as flood control which means that space for potential floods must be maintained even in dry years.
But state, federal and local water managers are working with scientists on strategies to reduce flood risk while reserving more water in California’s reservoirs.
Water managers at Lake Mendocino, for instance, are incorporating new weather forecasting tools to update decades-old guidelines governing when to hold onto water and when to release it. The strategy increased the lake’s storage by nearly 20% in 2020, with most of the water going to agriculture.